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So heres my issue. My trans sometimes engages into first with a thump and doesnt always downshift to first as precise as it was designed. Like the drive shaft isnt engaging right away and when it does theres my thump. Ive narrowed one possible solution down to low trans fluid. Now, What should I top off the low fluid with? Its still got a red color in it so I dont want to drain and refill. So not knowing what fluid is in it do I run a risk of malfunction topping off with "x" fluid? There is a slow trans leak but not bad enough to leaves a drop or puddle on the ground. Just looks lubricated for performance under there

Tranny fluids are generally interchangeable, although there's alot of superstition that they are not. I've mixed castrol dexron 3 mineral tranny oil with zf lifeguard synthetic tranny oil with no problems now for 3 years. So I suggest that you just top up with whatever was correctly rated for your transmission according to the Bentley manual, or its equivalents as you discover them to be when you google around for the info. Don't be concerned about mixing oils.

Check the troubleshooting tables attached for more info on probable causes and solutions to your tranny's symptoms.

Question:
Does Mobil 1 Synthetic ATF Meet the Requirements for ZF Transmissions?
I have found out that Mobil is recommending the Mobil 1 Synthetic ATF as a replacement for the Esso LT 71141 ATF used in BMW transmissions. I have a 1998 BMW 750iL with a ZF 5HP30 transmission, does Mobil Oil guarantee this product as meeting all the requirements of the ZF transmission?
-- McGarvey Cline II, Gainesville, FL

Answer:
No. We do not guarantee that the product meets all the requirements of ZF transmissions, which are very extensive depending on the transmission type/model year. ExxonMobil does say that this product is suitable for use in this application based on the type and quality of the recommended fluid, Esso LT 71141.

Use non-approved fluids at your own risk, seems to be the stance of the oil company

I think the correct advice is to top off the fluid using what is spec'd for the specific trans.

Ill grab some approved fluid. The tranny only does its little issue when I brake and go to accelerate, say come up to a light and slow down then light turns green with out fully stopping. If its a rebuild I guess I pull and rebuild it. I have a couple guys who rebuild autos so they can teach/assist me with it. Im sure it wont be as easy as my 6sp audi rebuild I did. But I always like to learn new things

Thanks man! Im gonna check the fluid level in the next day or 2. I just got my home shop back from a shady renter so I can play at home now instead of at work having to be done with projects by quitting time due to my gf not having a car and relying on me every day........ I appreciate your help and responses to all my questions. I know forums get repetitive with the same questions over and over again.

Thanks man! Im gonna check the fluid level in the next day or 2. I just got my home shop back from a shady renter so I can play at home now instead of at work having to be done with projects by quitting time due to my gf not having a car and relying on me every day........ I appreciate your help and responses to all my questions. I know forums get repetitive with the same questions over and over again.

Please try the quick and dirty test I referred to above first before you do a formal check on fluid levels. And if you do eventually find that levels are underfilled, you need to check very carefully to see if you have a leak anywhere from the tranny itself to the oil lines going from the transmission to the radiator and back.

Question:
Does Mobil 1 Synthetic ATF Meet the Requirements for ZF Transmissions?
I have found out that Mobil is recommending the Mobil 1 Synthetic ATF as a replacement for the Esso LT 71141 ATF used in BMW transmissions. I have a 1998 BMW 750iL with a ZF 5HP30 transmission, does Mobil Oil guarantee this product as meeting all the requirements of the ZF transmission?
-- McGarvey Cline II, Gainesville, FL

Answer:
No. We do not guarantee that the product meets all the requirements of ZF transmissions, which are very extensive depending on the transmission type/model year. ExxonMobil does say that this product is suitable for use in this application based on the type and quality of the recommended fluid, Esso LT 71141.

Use non-approved fluids at your own risk, seems to be the stance of the oil company

I think the correct advice is to top off the fluid using what is spec'd for the specific trans.

So they say its the same as Esso LT, but they just won't guarantee it ? That sounds like a contradiction? From Exxonmobil? How could that be ?

Perhaps its because they did not manufacture the transmission or did not feel bothered to put it through the 10,000 hours of tests, because they are not in the transmission business, and LT was the benchmark anyway.

In any case, the manual says specifically NOT to use Dex3 in my transmission. That's exactly what's in there right now, and has been so for the past 3 years, with absolutely no difference to the tranny's performance from the previous fluid, which I later realised was ZF Lifeguard. That was my pre mafia days when I didn't know the good from bad and had not encountered the bentley manual. The lifeguard was in good shape to boot. Damn.

So not only is Dex3 working fine in my car, it is also mixing with the 1-3 litres of zf lifeguard which would have been left in my torque convertor from the last oil change, and no mischief has resulted, and from a recent inspection of the oil's colour, its still good.

The moral of the story is that nothing beats independent research, common sense, gut instinct, and reading about people's varied experiences widely, asking questions, and cogitating all of that. Not everyone sees the value of such a temperament.

Zahnradfabrik Friedrichshafen (ZF) manufactures automatic transmissions for passenger car and commercial vehicles. To be listed, the additive company must have initially gained ZF approval on the additive system. This involves ZF in-house testing (including friction testing) and field trials.

Listing for both passenger car automatic transmissions (ZF TE-ML 11) and commercial vehicle automatic transmissions (ZF TE-ML 14) requires that the ATF use a ZF approved additive system and have either DEXRONŽ IID or DEXRONŽ III approval. It then must meet the ZF listing criteria detailed in the application form. This includes viscosity, shear stability and scuffing protection

Dex 3 is approved for your car, by the manufacturer..... you rebel you.

You should ad the ZF additive if you can find it. It will help your trans last longer, and work better.

One more reason to follow the reccomendations would be warranty claims. I had a new truck lose a transmission. We had serviced it at my friends shop. He called Chrysler and found out we had to use a mopar additive when we flushed the trans every 30k miles. The fan clutch failed, the trans overheated. At first the dealer tried to deny repairs on the trans and only wanted to cover the failed fan clutch. We had the records to back up using the correct fluid and service interval, it saved me $4000.

I have run Amsoil extensively, some RP and some Redline. None of them ever really impressed me, even though I need to try MTL in my 535. I know some like to try and reinvent the wheel. I accept that engineers with far more training and experience than I already figured it out.

It looks to me that the leak was on or near the radiator and has been fixed previous to my ownership. There was trans fluid all over around the radiator. Im going to assume there fix was to stop the leak and may have found it to difficult to put the car up and top off the fluid. Everything is dry all around the trans and all the lines. I pressured washed everything with the bumper off and havnt seen any leaks yet.

It looks to me that the leak was on or near the radiator and has been fixed previous to my ownership. There was trans fluid all over around the radiator. Im going to assume there fix was to stop the leak and may have found it to difficult to put the car up and top off the fluid. Everything is dry all around the trans and all the lines. I pressured washed everything with the bumper off and havnt seen any leaks yet.

It goes to show that the average mechanic does not know how to correctly check transmission fluids on our cars, for surely they would have done that after fixing the leak and 1.5 quarts is a **** load of fluid to be lacking that's nearly 20% of what the tranny will take during a regular oil change.

Or maybe the po fixed this quickly before selling it off to you and didn't want to spend more money basterds.

Lol works for me! Glad things work that way. I have about 5 hrs in an engine swap for it. So a few maintenance things is no sweat. It has a new radiator and the head gasket and engine rebuild has been done as well. I just found this out yesterday it was a friend of mines dads and he just gave me a bunch of receipts for the last 5-6 years.